Process for making dialkyl ethers from alcohols

Abstract

Processes for preparing dialkyl ethers from C 4 to C 8 straight-chain alcohols using an ionic liquid.

1 . A process for the preparation of a dialkyl ether in a reaction mixture comprising (a) contacting at least one C 4  to C 8  straight-chain alcohol with at least one homogeneous acid catalyst in the presence of at least one ionic liquid to form (i) a dialkyl ether phase of the reaction mixture that comprises a dialkyl ether, and (ii) an ionic liquid phase of the reaction mixture; and (b) separating the dialkyl ether phase of the reaction mixture from the ionic liquid phase of the reaction mixture to recover a dialkyl ether product; wherein an ionic liquid is represented by the structure of the following formula 
     
       
         
         
             
             
         
       
     
     wherein:
 in the cation, Z is —(CH 2 ) n — where n is an integer from 2 to 12; and R 2 , R 3  and R 4  are each independently selected from the group consisting of H, —CH 3 , —CH 2 CH 3 , and C 3  to C 6  straight-chain or branched monovalent alkyl radicals; and 
 A −  is an anion selected from the group consisting of [CH 3 OSO 3 ] − , [C 2 H 5 OSO 3 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [CF 3 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N] − , and [(CF 3 CFHCF 2 SO 2 ) 2 N] − . 
 
   
   
       2 . The process of  claim 1 , wherein a homogeneous acid catalyst is a homogeneous acid catalyst having a pKa of less than about 4. 
   
   
       3 . The process of  claim 1 , wherein the reaction mixture comprises an ionic liquid in an amount of about 0.1% or more, and yet in an amount of about 25% or less, by weight relative to the weight of the C 4  to C 8  alcohol present therein. 
   
   
       4 . The process of  claim 1 , wherein a homogeneous acid catalyst is selected from the group consisting of inorganic acids, organic sulfonic acids, heteropolyacids, fluoroalkyl sulfonic acids, metal sulfonates, metal trifluoroacetates, compounds thereof and combinations thereof. 
   
   
       5 . The process of  claim 1 , wherein a homogeneous acid catalyst is selected from the group consisting of sulfuric acid, fluorosulfonic acid, phosphorous acid, p-toluenesulfonic acid, benzenesulfonic acid, phosphotungstic acid, phosphomolybdic acid, trifluoromethanesulfonic acid, nonafluorobutanesulfonic acid, 1,1,2,2-tetrafluoroethanesulfonic acid, 1,1,2,3,3,3-hexafluoropropanesulfonic acid, bismuth triflate, yttrium triflate, ytterbium triflate, neodymium triflate, lanthanum triflate, scandium triflate, and zirconium triflate. 
   
   
       6 . The process of  claim 1 , wherein the reaction mixture comprises a catalyst in an amount of about 0.1% or more, and yet in an amount of about 20% or less, by weight relative to the weight of the C 4  to C 8  alcohol present therein. 
   
   
       7 . The process of  claim 1 , wherein said C 4  to C 8  straight-chain alcohol is selected from the group consisting of n-butanol, n-pentanol, n-hexanol, n-heptanol and n-octanol. 
   
   
       8 . The process of  claim 1 , wherein said C 4  to C 8  straight-chain alcohol is n-butanol and said dialkyl ether is dibutyl ether. 
   
   
       9 . The process of  claim 1 , which is carried out under an inert atmosphere. 
   
   
       10 . The process of  claim 1 , wherein the dialkyl ether product is in the vapor phase. 
   
   
       11 . The process of  claim 1 , wherein the ionic liquid phase comprises catalyst residue. 
   
   
       12 . The process of  claim 1 , wherein the separated ionic liquid phase is recycled to the reaction mixture. 
   
   
       13 . The process of  claim 1 , wherein water is removed from the separated ionic liquid phase. 
   
   
       14 . The process of  claim 1 , wherein the C 4  to C 8  straight-chain alcohol is n-butanol, wherein forming the reaction mixture occurs at a temperature of from about 50 degrees C. to about 300 degrees C. and a pressure of from about 0.1 MPa to about 20.7 MPa. 
   
   
       15 . The process of  claim 1 , wherein the C 4  to C 8  straight-chain alcohol is n-butanol, wherein forming the reaction mixture occurs at a temperature of from about 50 degrees C. to about 300 degrees C. and a pressure of from about 0.1 MPa to about 20.7 MPa, and an ionic liquid is 1-(2-N,N,N-dimethylpropylaminoethyl)-5-methyl-pyrrolidine-2-one 1,1,2,2-tetrafluoroethanesulfonate. 
   
   
       16 . The process of  claim 1 , wherein the C 4  to C 8  straight-chain alcohol is n-butanol, wherein forming the reaction mixture occurs at a temperature of from about 50 degrees C. to about 300 degrees C. and a pressure of from about 0.1 MPa to about 20.7 MPa, wherein an ionic liquid is 1-(2-N,N,N-dimethylpropylaminoethyl)-5-methyl-pyrrolidine-2-one 1,1,2,2-tetrafluoroethanesulfonate, and a homogeneous acid catalyst is 1,1,2,2-tetrafluoroethanesulfonic acid.